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l  oited  States  Dep^wiSS^'lgriculture, 

BUREAU  OF  ENTOMOLOGY. 
I  .  i  i.   HOWARD.  I  ntomologUi  tnd  Chid  <•(  D 


Circular  No  146. 


THE    MOVKMKNT   Of  THE    HEXICAN    COTTON    BOLI 
nt.iyil  in  1911. 

By  \V.  l».  in  n 
In  Charge  of  Southern  Field  Crop  Insect  Invent  iff  dlionT. 

Daring  the  Reason  <>f  1911  the  boL  weevil  was  greatly  reduced  in 
lumbers  throughout  its  entire  range.  This  resulted  from  a  com- 
bination of  climatic  influences  extending  over  a  period  of  about 
tlnvc  year-.  So  unfavorable  were  the  conditions  that  the  insect 
was  exterminated  in  an  urea  covering  about  23,000  square  miles  in 
the  northwestern  portion  <>f  Texas  and  the  western  portion  of  Okla- 
homa. Undoubtedly  these  conditions  had  an  important  bearing  on 
the  production  of  the  large  crop  of  1911. 

The  unfavorable  condition-  for  the  weevil  which  culminated  in 
1911  began  in  L909.  In  that  year  drought  occurred  in  Texas  and 
Louisiana  at  such  a  time  a>  to  check  the  development  of  the  imma- 
ture stages.  In  1910  equally  adverse  conditions  prevailed,  and  the 
pe-t  was  further  reduced  in  numbers.  At  the  end  of  the  season  of 
1910  condition-  arose  which  gave  the  insect  another  very  important 
■etback.  This  was  a  killing  frost  which  occurred  October  29.  The 
Weevils  were  deprived  of  their  food  in  all  parts  of  the  infested  terri- 
tory except  along  the  Gulf  Coast  and  in  a  few  isolated  localities  else- 
where.  The  freeze  destroyed  outright  enormous  numbers  of  the 
ils  which  wire  found  in  the  bolls  and  squares,  but  the  conditions 
immediately  following  the  freeze  were  even  more  Important  in  re- 
ducing the  infestation  to  a  very  low  point.  After  the  freeze  of  O  I 
tier  29  the  weather  became  warm,  and  this  induced  activity  on  the  part 
of  the  weevil-  that  survived.  In  fact,  temperature-  occurred  for 
several  week.-  which  caused  the  in-eci-  i  ire   food.     An  active 

search  for  food  began,  but  as  the  cotton  had  all  been  killed  the  ma- 
jority of  the  weevil-  which  had  survived  the  f"iveze  could  find  no 
food  and  perished.  •— ^      / 

(Mr.  140 — 12 


/ 


■    -• 
2  THE    MOV  KM  EST    OF    THE    ROLL    WEEVIL   IN    1911. 

The  general  effect  hi  Hie  cold  of  Oct  ok  -r  29  is  shown  by  a  study  of 
the  conditions  in  certain  localities  which  were  exempt  from  freezing 
temperatures.  In  several  counties  in  the  vicinity  of  Cisco,  Tex.,  for 
some  unexplained  reason,  the  first  killing  frost  in  1910  did  not  occur 
until  November  29.  At  this  time  m6s1  of  the  weevils  were  in  hiber- 
nating quarters.  As  a  result,  in  1911.  it  was  found  that  in  the  vicinity 
of  Brownwood  there  was  an  area  in  which  the  weevils  were  numerous 
and  in  Avhich  considerable  damage  was  done.  This  area  corresponded 
exactly  with  the  area  in  which  the  freeze  of  October  29  was  not 
experienced. 

The  great  reduction  in  the  number  of  weevils  which  succeeded  in 
passing  the  winter  of  1910-11  is  shown  by  hibernation  experiments 
which  were  conducted  at  Tallulah,  La.  At  this  place  it  is  determined 
that  one-half  of  1  per  cent  of  the  weevils  which  entered  hibernation 
emerged  in  the  spring  of  1911.  In  favorable  seasons  as  high  as  12 
per  cent  have  survived  in  that  locality  and,  in  fact,  the  average  sur- 
vival during  seven  different  seasons  in  seven  widely  separated  locali- 
ties in  Texas  and  Louisiana  has  been  7  per  cent. 

The  region  in  which  the  boll  weevil  became  exterminated  in  1911 
is  the  one  in  which  the  conditions  of  drought  were  most  intense  in 
1909  and  1910  and  in  which  at  the  same  time  the  conditions  for 
hibernation  are  less  favorable  than  in  other  parts  of  the  cotton  belt. 
The  territory  where  the  loss  occurred  consists  generally  of  open 
country  in  which  but  little  timber  is  to  be  found. 

Notwithstanding  the  great  reduction  in  the  numbers  of  the  boll 
weevils  in  the  United  States  in  1911  considerable  advance  was  made 
to  the  east  and  north  when  the  dispersion  movement  began  in  August. 
The  explanation  of  this  lies  in  the  outbreak  of  the  cotton  caterpillar, 
which  defoliated  practically  all  of  the  fields  throughout  the  infested 
area  at  about  the  time  the  dispersion  movement  was  beginning.  The 
weevils  started  on  their  dispersion  flight,  encountered  fields  which 
had  been  stripped  by  the  leaf  worm,  and  continued  their  flight  indefi- 
nitely. If  the  fields  just  beyond  the  border  of  the  previously  infested 
territory  had  not  been  defoliated  the  weevils  would  have  stopped  and 
the  total  area  covered  would  have  been  much  less. 

This  extensive  dispersion  of  the  insect  caused  it  to  regain  much  of 
the  territory  it  had  lost  in  Texas  and  Oklahoma,  and  Florida  became 
invaded  for  the  first  time.    (See  map,  fig.  1.) 

The  reasons  for  the  great  scarcity  of  weevils  in  1911  are  plain. 
The  reduction  was  due  to  a  combination  of  climatic  influences 
which  can  only  be  expected  to  recur  at  very  infrequent  intervals. 
With  the  return  of  seasons  favorable  to  it  the  boll  weevil  will  un- 
doubtedly regain  all  of  the  lost  territory  and  multiply  to  the  same 
extent  as  it  has  in  the  past.    It  must  not  be  supposed  from  the  situa- 


Ill  i     MOV1  \i  I  \ n  I     BOI  I.    WEEVIL    IN    1911. 


UNIVERSITY  OF  FLORIDA 


4 


3  1262  09216  5827 
THE    MOVEMENT    OF   THE   BOLL    ..  ~.~.*^   **,    ^^. 


tion  in  1911  that  there  is  any  hope  whatever  for  a  permanent  reduc- 
tion in  the  importance  of  the  boll  weevil.  On  the  contrary,  it  is  nec- 
essary for  planters  to  continue  their  fight  against  the  pest  according 
to  the  plans  that  have  been  detailed  in  the  publications  of  the  Depart- 
ment of  Agriculture. 

Approved: 

James  AVilson, 

Secretary  of  Agriculture. 

Washington,  D.  C.  January  3, 1912. 

o 


